Work vehicle

Abstract

A work vehicle according to the present disclosure comprises: a vehicle body; a plurality of wheels; a plurality of vehicle body support parts that are capable of changing a distance between the ground contact surface of each of wheels and the vehicle body; a plurality of hydraulic actuators that include a hydraulic actuator for vertical movement which drives the vehicle body support parts so as to change a vertical distance in order to maintain the vehicle body in a predetermined posture; a hydraulic pump that discharges hydraulic oil for operating each of the plurality of hydraulic actuators; a plurality of flow rate adjustment valves that adjust the flow rate of the hydraulic oil from the hydraulic pump to each of the hydraulic actuators; and a control device that controls each of the plurality of flow rate adjustment valves. The control device controls the flow rate adjustment valves so as to adjust the flow rate of the hydraulic oil supplied to the other hydraulic actuators after securing the required flow rate of the hydraulic oil required for operation of the hydraulic actuator for vertical movement.

Description

Work vehicle

[0001] This application claims priority to Japanese Patent Application No. 2024-103478, filed on June 27, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Document 1 discloses a work vehicle suitable for traveling on rough terrain. This work vehicle includes a vehicle body, multiple traveling wheels, multiple vehicle body supports, multiple hydraulic actuators, and a hydraulic pump. The multiple vehicle body supports are capable of changing the distance between the ground contact surface of each traveling wheel and the vehicle body so as to maintain the posture of the vehicle body. The multiple hydraulic actuators include hydraulic actuators that drive each vehicle body support, hydraulic actuators that rotate the traveling wheels relative to each vehicle body support, and hydraulic actuators that drive each traveling wheel. The hydraulic pump supplies hydraulic oil to each hydraulic actuator.

[0003] JP 2024-004328 A

[0004] In the above-mentioned work vehicle, hydraulic oil discharged from a hydraulic pump is supplied to each of the multiple hydraulic actuators, thereby operating each hydraulic actuator. However, in the above-mentioned work vehicle, the flow rate of hydraulic oil supplied to each of the multiple hydraulic actuators is not adequately managed. As a result, when the total flow rate of hydraulic oil used by these hydraulic actuators reaches the discharge flow rate of the hydraulic pump, the pressure of the hydraulic actuators that drive the vehicle body support parts drops. This makes it difficult to maintain the posture of the vehicle body, and there is a risk of the work vehicle tipping over. The present disclosure aims to provide a work vehicle that can appropriately control the flow rate of hydraulic oil supplied to each of the multiple hydraulic actuators and maintain the vehicle body in a predetermined posture.

[0005] The work vehicle of the present disclosure comprises a vehicle body, a plurality of wheels arranged on each of the left and right sides of the vehicle body, a plurality of vehicle body support parts that can change the distance between the contact surface of each of the wheels and the vehicle body, a plurality of hydraulic actuators including a vertical movement hydraulic actuator that drives the vehicle body support parts to change the distance in the vertical direction to maintain the vehicle body in a predetermined posture, a hydraulic pump that discharges hydraulic oil to operate each of the plurality of hydraulic actuators, a plurality of flow rate control valves that adjust the flow rate of hydraulic oil from the hydraulic pump to each of the hydraulic actuators, and a control device that controls each of the plurality of flow rate control valves, and the control device controls the flow rate control valves to adjust the flow rate of hydraulic oil supplied to the other hydraulic actuators after ensuring the required flow rate of hydraulic oil required to operate the vertical movement hydraulic actuator.

[0006] According to the present disclosure, the flow rate of hydraulic oil supplied to each of a plurality of hydraulic actuators can be appropriately controlled, and the vehicle body can be maintained in a predetermined attitude.

[0007] FIG. 1 is a side view showing a work vehicle according to an embodiment of the present disclosure. FIG. 2 is a plan view of the work vehicle. FIG. 3 is an explanatory diagram of a support mechanism. FIG. 4 is a control block diagram of the work vehicle. FIG. 5 is a hydraulic circuit diagram of the work vehicle. FIG. 6 is an explanatory diagram of flow rate control performed by a flow rate control unit. FIG. 7 is an explanatory diagram of flow rate control when the work vehicle is traveling on flat ground and on rough ground. FIG. 8 is an explanatory diagram of flow rate control using an operation priority when the work vehicle is traveling on rough ground and the total usage flow rate reaches the supplyable flow rate. FIG. 9 is an explanatory diagram of flow rate control using a weighting coefficient when the work vehicle is traveling on rough ground and the total usage flow rate reaches the supplyable flow rate.

[0008] <Outline of Embodiments of the Present Disclosure> The following is a description of outlines of embodiments of the present disclosure. (1) A work vehicle according to an embodiment includes a vehicle body, a plurality of wheels arranged on both the left and right sides of the vehicle body, a plurality of vehicle body support sections that can change the distance between the contact surfaces of the wheels and the vehicle body, a plurality of hydraulic actuators including a vertical movement hydraulic actuator that drives the vehicle body support sections to change the distance in the vertical direction to maintain the vehicle body in a predetermined attitude, a hydraulic pump that discharges hydraulic oil for operating each of the plurality of hydraulic actuators, a plurality of flow rate adjustment valves that adjust the flow rate of hydraulic oil from the hydraulic pump to each of the hydraulic actuators, and a control device that controls each of the plurality of flow rate adjustment valves, and the control device controls the flow rate adjustment valves to adjust the flow rate of hydraulic oil supplied to the other hydraulic actuators after ensuring the required flow rate of hydraulic oil required to operate the vertical movement hydraulic actuator.

[0009] In the above-described work vehicle, the control device controls the flow control valve to ensure the required flow rate of hydraulic oil necessary to operate the vertical movement hydraulic actuator to maintain the vehicle body in a predetermined attitude, and then adjusts the flow rate of hydraulic oil supplied to the other hydraulic actuators. As a result, even if the total flow rate of hydraulic oil used by the multiple hydraulic actuators reaches the discharge flow rate of hydraulic oil discharged by the hydraulic pump, the required flow rate of the vertical movement hydraulic actuator is ensured, making it possible to maintain the vehicle body in a predetermined attitude.

[0010] (2) In the work vehicle described in (1) above, it is preferable that the control device calculates a supplyable flow rate of hydraulic oil that can be supplied to the multiple hydraulic actuators from the discharge flow rate of hydraulic oil discharged from the hydraulic pump, calculates a total usage flow rate of hydraulic oil actually used by each of the multiple hydraulic actuators, and controls the flow control valve to adjust the flow rate of hydraulic oil supplied to the other hydraulic actuators so that the total usage flow rate does not exceed the supplyable flow rate. In this case, when adjusting the flow rate of hydraulic oil supplied to the other hydraulic actuators, it is possible to prevent the total usage flow rate of hydraulic oil actually used by each of the multiple hydraulic actuators from exceeding the supplyable flow rate of hydraulic oil that can be supplied from the hydraulic pump to the multiple hydraulic actuators.

[0011] (3) The work vehicle described in (2) above further includes a driving condition detection unit that detects the driving conditions of the work vehicle, and the multiple hydraulic actuators include, as the other hydraulic actuators, a forward / rearward movement hydraulic actuator that drives the vehicle body support unit to change the distance in the forward / rearward direction, a swing hydraulic actuator that turns the wheels relative to the vehicle body support unit, and a traveling hydraulic actuator that drives the wheels, and the control device preferably sets operation priorities for the forward / rearward movement hydraulic actuator, the swing hydraulic actuator, and the traveling hydraulic actuator according to the driving conditions detected by the driving condition detection unit, and controls the flow control valve to ensure a flow rate of hydraulic oil necessary to operate the hydraulic actuators with a high operation priority, while adjusting the flow rate of hydraulic oil supplied to the hydraulic actuators with a low operation priority. In this case, the flow rates of hydraulic oil supplied to the forward / rearward movement hydraulic actuator, the swing hydraulic actuator, and the traveling hydraulic actuator can be appropriately controlled according to the driving conditions of the work vehicle.

[0012] (4) In the work vehicle described in (3) above, it is preferable that, when the total usage flow rate reaches the supplyable flow rate, the control device reduces the flow rate of hydraulic oil secured for the hydraulic actuators in order from the hydraulic actuator with the lowest operation priority, and controls the flow control valve based on the reduced flow rate. In this case, the flow rate of hydraulic oil secured for the other hydraulic actuators is reduced in order from the hydraulic actuator with the lowest operation priority, so that the total usage flow rate can be prevented from exceeding the supplyable flow rate while preventing the operation of the hydraulic actuators with the highest operation priority from being restricted.

[0013] (5) In the work vehicle described in (4) above, it is preferable that, when the control device reduces the flow rate of hydraulic oil secured for the hydraulic actuator with the low operation priority to a lower limit value, the control device reduces the flow rate of hydraulic oil secured for the hydraulic actuator with the next lowest operation priority while maintaining the flow rate at the lower limit value, and controls the flow control valve based on the reduced flow rate. In this case, when the flow rate of hydraulic oil secured for the hydraulic actuator with the low operation priority is reduced, the reduced flow rate can be prevented from falling below the lower limit value.

[0014] (6) In the work vehicle described in any one of (3) to (5), the driving condition detection unit detects whether the road surface on which the work vehicle is traveling is flat or rough, and when the detection result of the driving condition detection unit indicates flat ground, the control device preferably sets the operation priority of the swing hydraulic actuator higher than the operation priorities of the forward / rearward movement hydraulic actuator and the traveling hydraulic actuator. In this case, when the work vehicle travels on flat ground, the flow rate of hydraulic oil required to operate the swing hydraulic actuator involved in the travel is ensured, thereby preventing the swing operation of the work vehicle from being restricted.

[0015] (7) In the work vehicle described in any one of (3) to (6), the driving condition detection unit preferably detects whether the road surface on which the work vehicle is traveling is flat or rough, and the control device preferably sets the operation priority of the forward / rearward movement hydraulic actuator higher than the operation priorities of the swing hydraulic actuator and the traveling hydraulic actuator when the driving condition detection unit detects that the road surface is rough. In this case, when the work vehicle is traveling on rough terrain, the flow rate of hydraulic oil required to operate the forward / rearward movement hydraulic actuator, which is involved in maintaining the attitude of the vehicle body, is ensured. This makes it possible to prevent restrictions on the operation of the forward / rearward movement hydraulic actuator in addition to the up / down movement hydraulic actuator, making it easier to maintain the vehicle body in a predetermined attitude.

[0016] (8) In the work vehicle described in (6) or (7), it is preferable that the control device relatively reduces the required flow rate secured for the vertical movement hydraulic actuator when the detection result of the driving condition detection unit indicates flat ground, and relatively increases the required flow rate secured for the vertical movement hydraulic actuator when the detection result of the driving condition detection unit indicates rough ground. In this case, when the work vehicle is traveling on flat ground, the required flow rate of hydraulic oil secured for the vertical movement hydraulic actuator decreases, making it possible to increase the flow rate of hydraulic oil to other hydraulic actuators. Furthermore, when the work vehicle is traveling on rough ground, the required flow rate of hydraulic oil secured for the vertical movement hydraulic actuator increases, making it possible to reliably maintain the vehicle body in a predetermined attitude.

[0017] (9) In the work vehicle described in any one of (3) to (8), it is preferable that the traveling condition detection unit includes an operation switch for switching the traveling speed of the work vehicle between high and low speeds, and that when the operation switch is switched to high speed, the control device sets the operation priority of each of the traveling hydraulic actuator and the swing hydraulic actuator to be higher than the operation priority of the forward / rearward movement hydraulic actuator. In this case, when the work vehicle travels at high speed, the flow rate of hydraulic oil required for the operation of each of the traveling hydraulic actuator and the swing hydraulic actuator involved in the travel is ensured, thereby preventing restrictions on high-speed traveling and swinging operations of the work vehicle.

[0018] (10) In the work vehicle described in any one of (3) to (9), the traveling condition detection unit preferably includes an operation switch for switching the traveling speed of the work vehicle between high and low speeds, and when the operation switch is switched to low speed, the control device preferably sets the operation priority of the forward / rearward movement hydraulic actuator higher than the operation priorities of the swing hydraulic actuator and the traveling hydraulic actuator. In this case, when the work vehicle is traveling at low speed, the flow rate of hydraulic oil necessary for the operation of the forward / rearward movement hydraulic actuator, which is involved in maintaining the attitude of the vehicle body, is ensured. This makes it possible to prevent restrictions on the operation of the forward / rearward movement hydraulic actuator in addition to the up / down movement hydraulic actuator, making it easier to maintain the vehicle body in a predetermined attitude.

[0019] <Details of the embodiment> Preferred embodiments will now be described with reference to the drawings. [Overall configuration of the work vehicle] Fig. 1 is a side view showing a work vehicle 10 according to an embodiment of the present disclosure. Fig. 2 is a plan view of the work vehicle 10. The work vehicle 10 shown in Figs. 1 and 2 is a vehicle capable of traveling on uneven road surfaces (uneven terrain).

[0020] In the following description, the direction of the arrow FW shown in the figure is the "front" of the work vehicle 10, which is the straight-ahead direction of the work vehicle 10. The direction of the arrow BK is the "rear" of the work vehicle 10, which is opposite to the straight-ahead direction. The direction of the arrow RH is the "right" of the work vehicle 10 moving straight, and the direction of the arrow LH is the "left" of the work vehicle 10 moving straight. The direction of the arrow DW is the "down" of the work vehicle 10, which is the road surface side, and the direction of the arrow UP is the "up" of the work vehicle 10, which is the opposite side to the road surface.

[0021] The work vehicle 10 has a vehicle body 11, a plurality of wheels 12, a plurality of support mechanisms 13, and a control device 17. The work vehicle 10 of this embodiment has four wheels 12 and the same number (four) of support mechanisms 13 as the wheels 12. The support mechanisms 13 connect the vehicle body 11 and the wheels 12. The wheels 12 are arranged at the front and rear of each of the left and right sides of the vehicle body 11. The number of wheels 12 is not limited to that of this embodiment, and may be two or more.

[0022] The vehicle body 11 has a frame 21. The vehicle body 11 has a loading section 22 on top of the frame 21, on which cargo can be loaded. The loading section 22 has a flat loading surface 221 on its upper surface. The loading surface 221 has a substantially rectangular shape in a plan view (see FIG. 2 ). The loading surface 221 is provided so as to extend in the left-right and front-rear directions. The cargo to be loaded is, for example, agricultural equipment, agricultural materials such as fertilizer and chemicals, harvested crops or harvest baskets, or pallets on which these are placed.

[0023] The multiple support mechanisms 13 are located at the left front, right front, left rear, and right rear of the vehicle body 11, respectively. The support mechanisms 13 are attached to the vehicle body 11 (part of the frame 21) and support the wheels 12 so that their positions can be changed relative to the vehicle body 11. The support mechanisms 13 have articulation link mechanisms 30 as operating parts that are operable to change the positions of the wheels 12. The wheels 12 are attached to the articulation link mechanisms 30. The support mechanisms 13 have attitude change actuators 14 that drive the articulation link mechanisms 30.

[0024] The attitude-changing actuator 14 operates the bending link mechanism 30 to change the attitude of the bending link mechanism 30. The attitude-changing actuator 14 of this embodiment has a first hydraulic cylinder 36 and a second hydraulic cylinder 37. The specific configurations of the support mechanism 13 and the attitude-changing actuator 14 will be described later.

[0025] The work vehicle 10 has a plurality of hydraulic motors 15. The hydraulic motors 15 are provided at the ends of the articulated linkages 30 together with the wheels 12. The hydraulic motors 15 are hydraulic actuators for traveling that drive the wheels 12 to rotate.

[0026] The wheels 12 are driven wheels that are rotated by hydraulic motors 15. The rotation of the wheels 12 causes the work vehicle 10 to move. The work vehicle 10 has a plurality of training wheels 16. The training wheels 16 are attached midway along the articulating link mechanism 30. The training wheels 16 are attached to the connecting portions (joint portions) of a first link 31 and a second link 32, which will be described later and which make up the articulating link mechanism 30. The training wheels 16 are driven wheels that can rotate freely.

[0027] The vehicle 10 has a hydraulic unit (hydraulic pressure supply source) 51, a battery 52, and an engine 53. The hydraulic unit 51 supplies hydraulic oil to a plurality of hydraulic actuators (hydraulic motor 15, first hydraulic cylinder 36, second hydraulic cylinder 37, and a swing cylinder 38, which will be described later) provided on the vehicle 10.

[0028] The hydraulic unit 51, battery 52, and control device 17 are mounted on the vehicle body 11 (frame 21), and in this embodiment (see FIG. 1), are located below the loading section 22. The battery 52 supplies power to the control device 17, hydraulic unit 51, and a plurality of sensors, which will be described later.

[0029] The hydraulic unit 51 has a hydraulic pump 54, a plurality of control valves 55, and a hydraulic oil tank 56. The hydraulic pump 54 is driven by the engine 53. The hydraulic pump 54 discharges hydraulic oil for operating the plurality of hydraulic actuators 15, 36, 37, and 38, respectively.

[0030] The plurality of control valves 55 are connected to the plurality of hydraulic actuators 15, 36, 37, and 38, respectively. The control valves 55 are proportional control solenoid valves that can adjust the flow rate of hydraulic oil. The control valves 55 start and stop the supply of hydraulic oil from the hydraulic pump 54, and also function as flow rate adjustment valves that adjust the flow rate of the hydraulic oil. The control device 17 controls the plurality of control valves 55, respectively, to adjust the flow rate of hydraulic oil from the hydraulic unit 51 to each of the hydraulic actuators 15, 36, 37, and 38.

[0031] The vehicle 10 has an operating handle 18 that is held by the worker, and an operating switch 19 that is manually operated by the worker. The operating handle 18 and the operating switch 19 are attached to a frame 21. The operating switch 19 has the function of switching the travel speed of the vehicle 10 between high and low speeds.

[0032] The control device 17 acquires an operation signal when the operation switch 19 is operated by the worker. When the control device 17 acquires an operation signal indicating that the operation switch 19 is in high speed, the control device 17 controls the control valve 55 connected to the hydraulic motor 15 so as to drive and rotate the multiple wheels 12 at high speed. When the control device 17 acquires an operation signal indicating that the operation switch 19 is in low speed, the control device 17 controls the control valve 55 connected to the hydraulic motor 15 so as to drive and rotate the multiple wheels 12 at low speed.

[0033] [Support Mechanism] The support mechanism 13 supports the wheels 12 so that they can be raised and lowered individually relative to the vehicle body 11. To this end, the support mechanism 13 has a bending link mechanism 30 as a vehicle body support section. Figure 3 is an explanatory diagram of the support mechanism 13. The bending link mechanism 30 has a first link 31 and a second link 32. Each of the first link 31 and the second link 32 is a linear member.

[0034] The vehicle body 11 has a fixed bracket 23 fixed to a part of the frame 21. A first end 311 of the first link 31 on the frame 21 side is supported by the fixed bracket 23 so as to be swingable around a first horizontal axis X1 in the left-right direction.

[0035] A first end 321 of the second link 32 is supported by a second end 312 of the first link 31 so as to be swingable about a second horizontal axis X2 in the left-right direction. A support bracket 33 is attached to the second end 322, which is the tip side of the second link 32. The wheel 12 is supported by the support bracket 33.

[0036] A pair of attitude-changing actuators 14 is provided for one articulating link mechanism 30 having a first link 31 and a second link 32. Each pair of attitude-changing actuators 14 has one first hydraulic cylinder 36 and one second hydraulic cylinder 37.

[0037] The first hydraulic cylinder 36 extends and retracts to swing the first link 31 around the first horizontal axis X1. The first hydraulic cylinder 36 changes the swing posture of the first link 31 relative to the vehicle body 11. The second hydraulic cylinder 37 extends and retracts to swing the second link 32 around the second horizontal axis X2. The second hydraulic cylinder 37 changes the swing posture of the second link 32 relative to the first link 31.

[0038] The control valve 55 connected to the first hydraulic cylinder 36 and the control valve 55 connected to the second hydraulic cylinder 37 are separate valves (see Figure 4), and the first hydraulic cylinder 36 and the second hydraulic cylinder 37 operate to extend and retract independently. Figure 4 is a control block diagram of the work vehicle 10. The extension and retraction operations of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 cause the articulating link mechanism 30 to bend and extend.

[0039] 3, for example, when the first hydraulic cylinder 36 extends or retracts while the second hydraulic cylinder 37 is stopped, the first link 31, the second link 32, and the wheel 12 swing together around the first horizontal axis X1 while maintaining a constant relative positional relationship. When the second hydraulic cylinder 37 extends or retracts while the first hydraulic cylinder 36 is stopped, the second link 32 and the wheel 12 swing together around the second horizontal axis X2 while maintaining a constant attitude of the first link 31 relative to the vehicle body 11.

[0040] A support bracket 33 that supports the wheel 12 is attached to the second link 32. The hydraulic motor 15 is mounted on the support bracket 33. The support bracket 33 is attached to a second end 322 of the second link 32 so as to be swingable around a vertical axis Y in the up-down direction.

[0041] The work vehicle 10 has a hydraulic cylinder 38 for changing the rolling direction of the wheel 12. The hydraulic cylinder 38 is attached between a part of the second link 32 and the support bracket 33. When the hydraulic cylinder 38 extends or retracts, the support bracket 33 and the wheel 12 swing (swivel) around the vertical axis Y. The extension and retraction of the swivel cylinder 38 changes the traveling direction of the work vehicle 10. Therefore, the hydraulic cylinder 38 functions as a swivel hydraulic actuator for swiveling the wheel 12 relative to the articulating link mechanism 30 (second link 32). Hereinafter, the hydraulic cylinder 38 will be referred to as the swivel cylinder 38.

[0042] As described above, the work vehicle 10 of this embodiment has four support mechanisms 13 (articulating link mechanisms 30), and each support mechanism 13 is provided with a set of attitude-changing actuators 14. The set of attitude-changing actuators 14 provided on one support mechanism 13 and the other set of attitude-changing actuators 14 provided on another support mechanism 13 are separate actuators, and each attitude-changing actuator 14 operates independently. As a result, the four wheels 12 can be raised and lowered individually relative to the vehicle body 11 via each articulating link mechanism 30. Furthermore, the four articulating link mechanisms 30 make it possible to change the positions of the four wheels 12 relative to the vehicle body 11.

[0043] The bending link mechanism 30 can change the distance between the ground contact surface of the wheel 12 and the vehicle body 11 by its operation. The distance is the distance between the ground contact surface of the wheel 12 and the support position (first horizontal axis X1) of the support mechanism 13 on the vehicle body 11.

[0044] Of the attitude changing actuators 14 that operate the articulating link mechanism 30, the second hydraulic cylinder 37 is the hydraulic actuator most involved in maintaining the vehicle body 11 in a predetermined attitude. The second hydraulic cylinder 37 functions as a vertical movement hydraulic actuator that drives the articulating link mechanism 30 (second link 32) to change the vertical distance between the ground contact surface of the wheel 12 and the vehicle body 11. The vertical distance is the vertical distance between the ground contact surface of the wheel 12 and the support position of the vehicle body 11.

[0045] The first hydraulic cylinder 36 is the hydraulic actuator most involved in the center of gravity position control, which will be described later. The first hydraulic cylinder 36 functions as a longitudinal movement hydraulic actuator that drives the articulating link mechanism 30 (first link 31) so as to change the longitudinal distance between the ground contact surface of the wheel 12 and the vehicle body 11. The longitudinal distance is the distance between the ground contact surface of the wheel 12 and the support position of the vehicle body 11.

[0046] [Sensors] The vehicle 10 is equipped with multiple sensors. Figure 4 is a control block diagram of the vehicle 10, and mainly shows the configuration related to the left front support mechanism 13. Although the configuration of the other support mechanisms 13 is omitted in Figure 4, they have the same configuration as the left front support mechanism 13.

[0047] A head-side pressure sensor S1 and a rod-side pressure sensor S2 are connected to the second hydraulic cylinder 37. The head-side pressure sensor S1 detects the internal pressure of an oil chamber on the head side of the second hydraulic cylinder 37. The rod-side pressure sensor S2 detects the internal pressure of an oil chamber on the rod side of the second hydraulic cylinder 37. The control device 17 acquires the detection signals of the sensors S1 and S2.

[0048] A stroke sensor S3 that detects the amount of extension / contraction is provided in each of the first hydraulic cylinder 36 and the second hydraulic cylinder 37. The amount of extension / contraction of each of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 is related to the swing position of each of the first link 31 and the second link 32. Therefore, the detection value of the stroke sensor S3 is correlated with the swing position of each of the first link 31 and the second link 32. The detection value of the stroke sensor S3 makes it possible to uniquely detect the position of the wheel 12 relative to the vehicle body 11. The control device 17 acquires the detection signal of the stroke sensor S3 and can detect the position of the wheel 12.

[0049] The vehicle body 11 is provided with an inclination sensor S4 that detects the inclination state of the vehicle body 11. The inclination sensor S4 is configured using an inertial measurement unit (IMU), which is a well-known configuration. The IMU of this embodiment has a triaxial acceleration sensor and a gyro sensor, and detects changes in the attitude of the vehicle body 11, specifically, tilt in the front-rear and left-right directions. The control device 17 acquires the detection signal of the inclination sensor S4.

[0050] A rotation sensor S5 that detects the rotation speed of the wheel 12 is provided near the wheel 12. The control device 17 acquires a detection signal from the rotation sensor S5. Based on the detection value of the rotation sensor S5, the control device 17 controls the supply of hydraulic oil to the hydraulic motor 15 so that the rotation speed of the wheel 12 reaches a target value.

[0051] The work vehicle 10 has a pressure sensor S6 that detects the pressure of the hydraulic oil supplied to the hydraulic motor 15. The control device 17 acquires the detection signal of the pressure sensor S6. Based on the pressure of the hydraulic oil detected by the pressure sensor S6, the control device 17 controls the supply (pressure) of hydraulic oil to the hydraulic motor 15 so that the drive torque of the wheels 12 becomes a target value.

[0052] A stroke sensor S7 capable of detecting the amount of extension and contraction is provided on each of the four swing cylinders 38. The control device 17 receives the detection signal from the stroke sensor S7 and controls the traveling direction of the vehicle 10.

[0053] [Control Device] The control device 17 has an ECU 171 (Electronic Control Unit) that functions as a main control unit that controls the operation of the work vehicle 10. The ECU 171 has a microcomputer and executes various controls according to a control program. The ECU 171 has a non-volatile memory that stores programs corresponding to the functional units that execute the various controls, and a CPU that executes the programs. The functions (controls) of the functional units are realized by the CPU executing the programs.

[0054] The ECU 171 has an attitude control unit 172 as one of the functional units. The attitude control unit 172 executes horizontal control and center of gravity position control. The control device 17 (ECU 171) controls the attitude change actuator 14 to perform attitude control to maintain the vehicle body 11 in a predetermined attitude while traveling. Note that, in the following, the "predetermined attitude" will be described as an attitude in which the loading section 22 (loading surface 221) of the vehicle body 11 is horizontal (horizontal attitude), but it may also be an attitude other than horizontal.

[0055] (Horizontal Control) When the work vehicle 10 is traveling, the posture control unit 172 performs horizontal control based on the detection signal from the inclination sensor S4. Horizontal control is a control that operates the front, rear, left, and right support mechanisms 13 so that the loading unit 22 (loading surface 221) is in a horizontal position. Based on the detection signal from the inclination sensor S4, the posture control unit 172 determines the tilt angles in the front-rear direction and the left-right direction, with the vehicle main body 11 (loading unit 22) in a reference position in which the vehicle main body 11 is in a horizontal position. The posture control unit 172 controls the operation of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 so that these tilt angles become values ​​corresponding to the horizontal position (i.e., the tilt angles are zero).

[0056] The horizontal control will be further described. The ECU 171 calculates the target actuation amounts of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 required to bring the loading unit 22 to a horizontal position, based on the tilt attitude (tilt angle) of the loading unit 22 detected by the tilt sensor S4. The ECU 171 controls the actuation of each of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 so that the actual actuation amounts detected by the stroke sensor S3 become the target actuation amounts.

[0057] (Center of gravity position control) The posture control unit 172 is capable of performing center of gravity position control, which determines the center of gravity position of the vehicle body 11 based on the detection information of the inclination sensor S4 and the stroke sensor S3, and controls the operation of the support mechanism 13 so that the center of gravity position is located in the center of multiple (four) wheels 12 in a planar view.

[0058] The center of gravity position control will be further explained. The tilt state of the vehicle body 11 is detected by the output of the tilt sensor S4. The posture control unit 172 determines the tilt angle in the front-to-rear direction and the left-to-right direction from the horizontal posture of the vehicle body 11 based on the detection signal of the tilt sensor S4. The state of the support mechanism 13 (the angle of the first link 31 relative to the vehicle body 11, and the angle of the second link 32 relative to the first link 31) is detected based on the detection results of the extension / contraction amounts of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 detected by the multiple stroke sensors S3.

[0059] As a result, the attitude control unit 172 can obtain, through calculation, the overall attitude (inclined state) of the vehicle body 11 and the position of the center of gravity of the vehicle body 11 in relation to the ground contact positions of the four wheels 12. The attitude control unit 172 operates the first hydraulic cylinder 36 and the second hydraulic cylinder 37 so that the center of gravity thus obtained becomes the target attitude in which it is located in the center of the multiple (four) wheels 12 in a plan view.

[0060] In this way, center of gravity position control is control that adjusts the pressure (force) supporting the vehicle body 11 so that the center of gravity of the vehicle body 11 converges to the target center of gravity regardless of the unevenness of the road surface. As a variation of center of gravity position control, the attitude control unit 172 does not determine the center of gravity position of the vehicle body 11, but rather determines the ground contact pressure of multiple (four) wheels 12. The ground contact pressure is determined based on detection signals from pressure sensors S1 and S2. In this case, the attitude control unit 172 controls the operation of the support mechanism 13 so that the ground contact pressure of the wheels 12 on the lower side of the slope and the ground contact pressure of the wheels 12 on the upper side of the slope are equal.

[0061] The center of gravity position control makes it possible to generate driving force by aligning the wheels 12 with the unevenness of the road surface. By executing the horizontal control and center of gravity position control, the posture control unit 172 can operate the support mechanism 13 so that the loading unit 22 (placing surface 221) is in a horizontal position and so that all the wheels 12 generate driving force by aligning with the unevenness of the road surface.

[0062] [Hydraulic Circuit] Figure 5 is a hydraulic circuit diagram of the work vehicle 10. The hydraulic equipment groups (a set of hydraulic actuators 15, 36, 37, 38 and four control valves 55) corresponding to each of the four support mechanisms 13 of the work vehicle 10 are all configured identically, so Figure 5 only shows the hydraulic equipment group corresponding to one support mechanism 13. As shown in Figure 5, the work vehicle 10 is equipped with a supply oil passage 61, a discharge oil passage 65, an unload oil passage 81, and a relief oil passage 85.

[0063] The supply oil passage 61 has a main supply oil passage 62 connected to the hydraulic pump 54, and a plurality of branch supply oil passages 63 branching from the main supply oil passage 62 and connected to the four control valves 55 of each hydraulic equipment group. The discharge oil passage 65 has a main discharge oil passage 66 connected to the hydraulic oil tank 56, and a plurality of branch discharge oil passages 67 branching from the main discharge oil passage 66 and connected to the four control valves 55 of each hydraulic equipment group.

[0064] The four control valves 55 of each hydraulic equipment group include a control valve 551 connected to the hydraulic motor 15, a control valve 552 connected to the first hydraulic cylinder 36, a control valve 553 connected to the second hydraulic cylinder 37, and a control valve 554 connected to the swing cylinder 38. Each of the control valves 551, 552, 553, and 554 is a proportional control type three-position switching solenoid valve, and has a first solenoid 55a, a second solenoid 55b, a neutral position 55c, a first position 55d, and a second position 55e.

[0065] When the first solenoid 55a and the second solenoid 55b are de-energized, each of the control valves 551, 552, 553, and 554 is held in a neutral position 55c. In this state, no hydraulic oil flows between each of the control valves 551, 552, 553, and 554 and the corresponding hydraulic actuators 15, 36, 37, and 38. When the first solenoid 55a is energized, each of the control valves 551, 552, 553, and 554 switches from the neutral position 55c to a first position 55d, and when the second solenoid 55b is energized, the control valves 551, 552, 553, and 554 switch to a second position 55e.

[0066] The control valve 551 is connected to the hydraulic motor 15 via a forward rotation oil passage 71 and a reverse rotation oil passage 72. When the control valve 551 is switched to the first position 55d, hydraulic oil flows from the branched supply oil passage 63 to the forward rotation oil passage 71, and from the reverse rotation oil passage 72 to the branched discharge oil passage 67. This causes the hydraulic motor 15 to drive the wheels 12 in the forward direction, causing the vehicle 10 to move forward. At this time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the forward rotation oil passage 71 by adjusting the value of the current applied to the first solenoid 55a of the control valve 551.

[0067] When the control valve 551 is switched to the second position 55e, hydraulic oil flows from the branched supply oil passage 63 to the reverse rotation oil passage 72, and from the forward rotation oil passage 71 to the branched discharge oil passage 67. This causes the hydraulic motor 15 to drive the wheels 12 in the reverse direction, causing the vehicle 10 to move backward. At this time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the reverse rotation oil passage 72 by adjusting the value of the current applied to the second solenoid 55b of the control valve 551.

[0068] The control valve 552 is connected to the first hydraulic cylinder 36 via a head-side oil passage 73 and a rod-side oil passage 74. The head-side oil passage 73 is connected to an oil chamber on the head side of the first hydraulic cylinder 36. The rod-side oil passage 74 is connected to an oil chamber on the rod side of the first hydraulic cylinder 36.

[0069] When the control valve 552 is switched to the first position 55d, hydraulic oil flows from the branched supply oil passage 63 to the head-side oil passage 73, and from the rod-side oil passage 74 to the branched discharge oil passage 67. This causes the first hydraulic cylinder 36 to extend. At that time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the head-side oil passage 73 of the first hydraulic cylinder 36 by adjusting the value of the current applied to the first solenoid 55a of the control valve 552.

[0070] When the control valve 552 is switched to the second position 55e, hydraulic oil flows from the branched supply oil passage 63 to the rod-side oil passage 74, and from the head-side oil passage 73 to the branched discharge oil passage 67. This causes the first hydraulic cylinder 36 to contract. At that time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the rod-side oil passage 74 of the first hydraulic cylinder 36 by adjusting the value of the current applied to the second solenoid 55b of the control valve 552.

[0071] The control valve 553 is connected to the second hydraulic cylinder 37 via a head-side oil passage 75 and a rod-side oil passage 76. The head-side oil passage 75 is connected to an oil chamber on the head side of the second hydraulic cylinder 37. The rod-side oil passage 76 is connected to an oil chamber on the rod side of the second hydraulic cylinder 37.

[0072] When the control valve 553 is switched to the first position 55d, hydraulic oil flows from the branched supply oil passage 63 to the head-side oil passage 75, and from the rod-side oil passage 76 to the branched discharge oil passage 67. This causes the second hydraulic cylinder 37 to extend. At that time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the head-side oil passage 75 of the second hydraulic cylinder 37 by adjusting the value of the current applied to the first solenoid 55a of the control valve 553.

[0073] When the control valve 553 is switched to the second position 55e, hydraulic oil flows from the branched supply oil passage 63 to the rod-side oil passage 76, and from the head-side oil passage 75 to the branched discharge oil passage 67. This causes the second hydraulic cylinder 37 to contract. At that time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the rod-side oil passage 76 of the second hydraulic cylinder 37 by adjusting the value of the current applied to the second solenoid 55b of the control valve 553.

[0074] The control valve 554 is connected to the swing cylinder 38 via a head-side oil passage 77 and a rod-side oil passage 78. The head-side oil passage 77 is connected to an oil chamber on the head side of the swing cylinder 38. The rod-side oil passage 78 is connected to an oil chamber on the rod side of the swing cylinder 38.

[0075] When the control valve 554 is switched to the first position 55d, hydraulic oil flows from the branched supply oil passage 63 to the head-side oil passage 77, and from the rod-side oil passage 78 to the branched discharge oil passage 67. This causes the swing cylinder 38 to extend, and the wheels 12 to turn right (or left). At that time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the head-side oil passage 77 of the swing cylinder 38 by adjusting the current value applied to the first solenoid 55a of the control valve 554.

[0076] When the control valve 554 is switched to the second position 55e, hydraulic oil flows from the branched supply oil passage 63 to the rod-side oil passage 78, and from the head-side oil passage 77 to the branched discharge oil passage 67. This causes the swing cylinder 38 to contract, and the wheels 12 to turn left (or right). At that time, the control device 17 can adjust the flow rate of hydraulic oil supplied to the rod-side oil passage 78 of the swing cylinder 38 by adjusting the current value applied to the second solenoid 55b of the control valve 554.

[0077] One end of the unloading oil passage 81 is connected to the main supply oil passage 62 between the position where the hydraulic pump 54 and the branch supply oil passage 63 are connected. The other end of the unloading oil passage 81 is connected to the main discharge oil passage 66 between the position where the hydraulic oil tank 56 and the branch discharge oil passage 67 are connected. An unloading valve 82 is provided in the unloading oil passage 81.

[0078] One end of the relief oil passage 85 is connected to the main supply oil passage 62 between the connection position of the hydraulic pump 54 and the unload oil passage 81. The other end of the relief oil passage 85 is connected to the main discharge oil passage 66 between the connection position of the hydraulic oil tank 56 and the unload oil passage 81. A relief valve 86 is provided in the relief oil passage 85.

[0079] The unloading valve 82 is a two-position solenoid valve and has a solenoid 82a, a communication position 82b, and a cut-off position 82c. When the solenoid 82a is de-energized, the unloading valve 82 is held in the communication position 82b. When the unloading valve 82 is in the communication position 82b, the unloading oil passage 81 is in a communication state. In this communication state, the main supply oil passage 62 is connected to the hydraulic oil tank 56 via the unloading oil passage 81, the unloading valve 82 (communication position 82b), and the main discharge oil passage 66.

[0080] When the solenoid 82a is excited, the unloading valve 82 switches to the shutoff position 82c. When the unloading valve 82 is in the shutoff position 82c, the unloading oil passage 81 is shut off, and the connection between the main supply oil passage 62 and the hydraulic oil tank 56 is cut off.

[0081] When the hydraulic pump 54 is operating, the solenoid 82a is energized and the unloading valve 82 is in the shut-off position 82c. When the hydraulic pump 54 stops, the solenoid 82a is de-energized, the unloading valve 82 is switched to the communicating position 82b, and the hydraulic oil in the main supply oil passage 62 is discharged to the hydraulic oil tank 56.

[0082] The unloading valve 82 is configured to switch to maintain the temperature of the hydraulic oil within an appropriate temperature range (for example, a range from 60°C to 70°C). Specifically, when the temperature of the hydraulic oil falls below the appropriate temperature range, the solenoid 82a is excited and the unloading valve 82 switches to a shut-off position 82c. This increases the relief pressure, allowing the temperature of the hydraulic oil to rise to the appropriate temperature range.

[0083] If the temperature of the hydraulic oil rises above the optimum temperature range and the vehicle 10 is not operated for a predetermined period of time (e.g., a few seconds), the solenoid 82a is de-energized and the unloading valve 82 switches to the communicating position 82b. This allows the hydraulic oil to be returned to the hydraulic oil tank 56 to prevent the relief pressure from increasing, allowing the temperature of the hydraulic oil to drop to the optimum temperature range.

[0084] [Flow Control] In Figure 4, the ECU 171 of the control device 17 has a flow control unit 173 as one of the functional units. The flow control unit 173 executes flow control by controlling each control valve 551, 552, 553, and 554, which are flow adjustment valves, to adjust the flow rate of hydraulic oil supplied from the hydraulic pump 54 to each of the multiple hydraulic actuators 15, 36, 37, and 38. The multiple hydraulic actuators 15, 36, 37, and 38 are four hydraulic motors 15 (travel hydraulic actuators), four first hydraulic cylinders 36 (front-rear movement hydraulic actuators), four second hydraulic cylinders 37 (up-down movement hydraulic actuators), and four swing cylinders 38 (swing hydraulic actuators). The flow control unit 173 executes flow control in parallel with the attitude control of the attitude control unit 172 when the work vehicle 10 is traveling.

[0085] (Principles of flow rate control) Fig. 6 is an explanatory diagram of the flow rate control executed by the flow rate control unit 173. In Fig. 5 and Fig. 6, the flow rate control unit 173 ensures the flow rate of hydraulic oil necessary to maintain the vehicle body 11 in a predetermined attitude, and then adjusts the flow rate of hydraulic oil necessary for other operations.

[0086] The flow rate control unit 173 of this embodiment controls the flow rate (required flow rate) Q of hydraulic oil required to operate the four second hydraulic cylinders 37 that are most involved in maintaining the posture of the vehicle body 11. ３７ After ensuring this, the control valves 551, 552, 553, and 554 are controlled to adjust the flow rates of the hydraulic oil supplied to the other hydraulic actuators 15, 36, and 38.

[0087] The flow rate control unit 173 determines the flow rate required for the operation of each of the four second hydraulic cylinders 37 in the above-mentioned horizontal control and center-of-gravity position control, and calculates the sum of these flow rates as the required flow rate Q ３７The flow rate control unit 173 secures the required flow rate Q ３７ The four control valves 553 corresponding to the respective second hydraulic cylinders 37 are controlled so as to adjust the flow rate of the hydraulic oil supplied to each of the four second hydraulic cylinders 37 within the range of . This makes it possible to maintain the vehicle body 11 in a predetermined position (horizontal position).

[0088] The flow rate control unit 173 determines the required flow rate Q ３７ After ensuring the total usage flow rate Q, the flow rate of the hydraulic oil supplied to the other hydraulic actuators 15, 36, 38 except for the second hydraulic cylinder 37 is adjusted. ｕｓｅ is the supplyable flow rate Q ｓｕｐ The control valves 551, 552, and 554 corresponding to the other hydraulic actuators 15, 36, and 38 are controlled within a range not exceeding .

[0089] Available flow rate Q ｓｕｐ is the flow rate of hydraulic oil that can be supplied to all of the hydraulic actuators 15, 36, 37, and 38 out of the discharge flow rate of hydraulic oil discharged from the hydraulic pump 54. ｓｕｐ is preset to, for example, 80% of the discharge flow rate.

[0090] Total flow rate Q ｕｓｅ is the total flow rate of hydraulic oil actually used by all the hydraulic actuators 15, 36, 37, and 38. In other words, the total used flow rate Q ｕｓｅ is the flow rate Q of hydraulic oil actually used in the hydraulic motor 15 ｍ and the actual flow rate Q of the hydraulic oil used in each hydraulic cylinder 36, 37, 38. ｓ This is the combined flow rate of

[0091] Usage flow rate Q ｍ is the secured flow rate Q １５ (described later) is the flow rate of hydraulic oil actually used in the hydraulic motor 15, and Q １５ ≧Q ｍ The flow rate Q ｓ is the secured flow rate Q ３６ (see below), Q ３７ , Q ３８The flow rate of hydraulic oil actually used in each hydraulic cylinder 36, 37, 38 is within the range of (described later). ｓ Is, Q ３６ ≧Q ｓ Similarly, the flow rate Q of the second hydraulic cylinder 37 is ｓ Is, Q ３７ ≧Q ｓ and the flow rate Q of the rotating cylinder 38 is ｓ Is, Q ３８ ≧Q ｓ From the above, the total flow rate Q ｕｓｅ (Q １５ +Q ３６ +Q ３７ +Q ３８ ) ≧ Q ｕｓｅ The total flow rate Q ｕｓｅ But (Q １５ +Q ３６ +Q ３７ +Q ３８ ) = Q ｕｓｅ In other words, Q １５ =Q ｍ , Q ３６ =Q ｓ , Q ３７ =Q ｓ , Q ３８ =Q ｓ This shows the case where

[0092] The flow rate control unit 173 determines the usage flow rate Q ｍ is calculated based on the capacity (known) and rotation speed of the hydraulic motor 15. This rotation speed is measured using a rotation sensor. The rotation sensor may be a rotation sensor S5 that detects the rotation speed of the wheels 12, or a dedicated rotation sensor provided in the hydraulic motor 15. The flow rate control unit 173 calculates the used flow rate Q ｓ is calculated based on the capacity (known) and operating speed of each of the hydraulic cylinders 36, 37, 38. The operating speed is measured using stroke sensors S3, S7 provided on each of the hydraulic cylinders 36, 37, 38.

[0093] The flow rate control unit 173 calculates the total usage flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐThe corresponding control valves 551, 552, and 554 are controlled so that the hydraulic oil is distributed to the other hydraulic actuators 15, 36, and 38, respectively, within a range not exceeding .

[0094] (Flow rate control according to driving conditions) The vehicle 10 is equipped with a driving condition detection unit that detects the driving conditions of the vehicle itself. The driving condition detection unit in this embodiment is equipped with the tilt sensor S4 and the operation switch 19 described above. The tilt sensor S4 detects whether the road surface on which the vehicle 10 is driving is flat or rough. Specifically, the tilt sensor S4 detects whether the tilt angle of the vehicle body 11 in the longitudinal and lateral directions is small (flat) or large (rough)

[0095] The driving condition detection unit that detects whether the road surface is flat or rough may be an external sensor that senses the conditions outside the vehicle 10, other than the tilt sensor S4. Examples of external sensors include a LiDAR sensor, a camera, an image sensor, a laser range finder (range sensor), an ultrasonic sensor, a millimeter-wave radar, and a magnetic sensor.

[0096] The operation switch 19 detects whether the traveling speed of the vehicle 10 is high or low. Specifically, the operation switch 19 outputs (detects) either an operation signal indicating high speed or an operation signal indicating low speed, depending on the operator's switching operation. The flow rate control unit 173 acquires the operation signal output by the operation switch 19.

[0097] The flow control unit 173 sets the operation priority of the hydraulic actuators 15, 36, 38 other than the second hydraulic cylinder 37 in accordance with the traveling conditions of the vehicle 10 detected by the traveling condition detection unit (inclination sensor S4 and operation switch 19). The flow control unit 173 of this embodiment sets the operation priority order of the other hydraulic actuators 15, 36, 38 as the operation priority.

[0098] Specifically, when the detection result of the inclination sensor S4 indicates flat ground, the flow rate control unit 173 sets the operation priority of the four swing cylinders 38 higher than the operation priority of the four first hydraulic cylinders 36 and the four hydraulic motors 15. The operation priority of the four first hydraulic cylinders 36 and the four hydraulic motors 15 may be set higher for the former or may be set higher for the latter.

[0099] When the detection result of the tilt sensor S4 indicates that the terrain is rough, the flow rate control unit 173 sets the operation priority of the four first hydraulic cylinders 36 higher than the operation priority of the four slewing cylinders 38 and the four hydraulic motors 15. The operation priority of the four slewing cylinders 38 and the four hydraulic motors 15 may be set higher for the former or the latter.

[0100] When the operation switch 19 is switched to high speed and the flow rate control unit 173 receives an operation signal indicating high speed from the operation switch 19, the flow rate control unit 173 sets the operation priority of each of the four swing cylinders 38 and the four hydraulic motors 15 higher than the operation priority of the four first hydraulic cylinders 36. The operation priority of the four swing cylinders 38 and the four hydraulic motors 15 may be set higher for the former or the latter.

[0101] When the operation switch 19 is switched to low speed and the flow rate control unit 173 receives an operation signal indicating low speed from the operation switch 19, the flow rate control unit 173 sets the operation priority of the four first hydraulic cylinders 36 higher than the operation priority of the four swing cylinders 38 and the four hydraulic motors 15. The operation priority of the four swing cylinders 38 and the four hydraulic motors 15 may be set higher for the former or higher for the latter.

[0102] In the flow rate control, the flow rate control unit 173 controls the control valves 551, 552, and 554 corresponding to the other hydraulic actuators 15, 36, and 38 based on the set operation priority. In this case, the flow rate control unit 173 controls the control valves 551, 552, and 554 so as to ensure the flow rate of hydraulic oil necessary for the operation of the hydraulic actuators with high operation priority, and then adjust the flow rate of hydraulic oil supplied to the hydraulic actuators with low operation priority.

[0103] The flow control based on the operation priority is the same regardless of whether the vehicle 10 is traveling on flat ground, rough ground, at high speed, or at low speed, except that the operation priority differs. Figure 6 shows the flow control based on the operation priority when the vehicle 10 is traveling on rough ground. This flow control will be explained below, and explanations of the flow control when the vehicle 10 is traveling on flat ground, at high speed, or at low speed will be omitted.

[0104] 6 shows flow control in the case where the operation priority on rough ground is set in the order of highest to lowest: four first hydraulic cylinders 36, four swing cylinders 38, and four hydraulic motors 15. First, the flow control unit 173 determines the flow rate required for the operation of each of the four first hydraulic cylinders 36 with the highest operation priority, and calculates the sum of these flow rates as a flow rate Q ３６ Then, the flow rate control unit 173 secures the secured flow rate Q ３６ The four control valves 552 corresponding to the four first hydraulic cylinders 36 are controlled so as to adjust the flow rate of the hydraulic oil supplied to each of the four first hydraulic cylinders 36 within the range.

[0105] Next, the flow rate control unit 173 controls the flow rate Q ３６ After ensuring this, the flow rate required for the operation of each of the four rotation cylinders 38 with the next highest priority is determined, and the sum of these flow rates is calculated as the flow rate Q ３８ The flow rate control unit 173 secures the secured flow rate Q ３８ The four control valves 554 corresponding to the four rotary cylinders 38 are controlled so as to adjust the flow rate of the hydraulic oil supplied to each of the four rotary cylinders 38 within the range.

[0106] Next, the flow rate control unit 173 controls the flow rate Q ３８ After ensuring this, the flow rates required to operate the four hydraulic motors 15 with the lowest operation priority are determined, and the sum of these flow rates is calculated as the flow rate Q １５ The four control valves 551 corresponding to the four hydraulic motors 15 are controlled so as to adjust the flow rate of the hydraulic oil supplied to each of the four hydraulic motors 15 within the range.

[0107] From the above, the flow rate control unit 173 determines the required flow rate Q ３７ After securing the flow rate Q, the other hydraulic actuators 36, 38, and 15 for which the operation priority is set are ３６ , Q ３８ , Q １５ At this time, the flow rate control unit 173 adjusts the flow rate of the hydraulic oil supplied within the range of the total usage flow rate Q actually used by all the hydraulic actuators 37, 36, 38, and 15. ｕｓｅ (≦Q ３７ +Q ３６ +Q ３８ +Q １５ ) is the supplyable flow rate Q ｓｕｐ The control valves 551, 552, and 554 are controlled so that the value does not exceed the threshold.

[0108] 7 is an explanatory diagram of flow rate control when the vehicle 10 is traveling on flat ground and on rough ground. ３７ and supplyable flow rate Q ｓｕｐ As shown in FIG. 7, the flow rate control unit 173 determines the required flow rate Q ３７ Specifically, when the detection result of the inclination sensor S4 indicates flat ground, the flow rate control unit 173 determines the required flow rate Q ３７ When the detection result of the inclination sensor S4 is that the ground is uneven, the required flow rate Q ３７ Increases the relative

[0109] When the traveling condition of the vehicle 10 changes from flat ground to rough ground (FIG. 7), the flow rate control unit 173 adjusts the required flow rate Q ３７ When the traveling condition of the vehicle 10 changes from rough ground to flat ground, the flow rate control unit 173 controls the four control valves 553 so as to gradually increase the required flow rate Q ３７ The four control valves 553 are controlled so as to gradually decrease the

[0110] In the flow rate control, the flow rate control unit 173 calculates the total usage flow rate Q ｕｓｅ (above) is the supplyable flow rate Q ｓｕｐWhen the operating priority reaches (as described above), the flow rate of hydraulic oil secured is reduced in order from the hydraulic actuator with the lowest operating priority, and the corresponding control valve is controlled based on the reduced flow rate. This control is the same whether the vehicle 10 is traveling on rough ground, flat ground, at high speed, or at low speed, except for the operating priority, so the following will explain the case where the vehicle 10 is traveling on rough ground as an example.

[0111] FIG. 8 shows the total flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐ 8 is an explanatory diagram of flow rate control using the operation priority when the flow rate Q of the hydraulic oil secured for all the hydraulic actuators 15, 36, 37, and 38 reaches ３７ , Q ３６ , Q ３８ , Q １５ The sum of these is the total flow rate Q ｕｓｅ 8 only shows the flow rate control of the hydraulic oil supplied to the hydraulic motor 15, which has the lowest operation priority, and the swing cylinder 38, which has the next lowest operation priority.

[0112] In FIG. 8, when the operation time of the work vehicle 10 is t1, the supplyable flow rate Q ｓｕｐ By reducing the total flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐ Then, the flow rate control unit 173 determines the flow rate Q of hydraulic oil to be secured for the four hydraulic motors 15 with the lowest operating priority. １５ The flow rate control unit 173 reduces the reduced flow rate Q １５ At this stage, the operation of each hydraulic motor 15 is limited, but the flow rate Q required for the operation of the remaining hydraulic actuators 36, 37, and 38 is controlled within the range of ３７ , Q ３６ , Q ３８ Therefore, the operation of the remaining hydraulic actuators 36, 37, and 38 is not restricted.

[0113] The flow rate control unit 173 controls the flow rate Q １５When the flow rate Q １５ The flow rate Q of hydraulic oil to be ensured for the four rotation cylinders 38 with the next lowest operating priority while maintaining the ３８ Then, the flow rate control unit 173 reduces the reduced flow rate Q ３８ Based on this, the four corresponding control valves 554 are controlled. The lower limit of the flow rate is the flow rate required to operate the hydraulic actuator (here, hydraulic motor 15) within the minimum range that does not interfere with the operation of the work vehicle 10.

[0114] The flow rate control unit 173 reduces the flow rate Q ３８ At this stage, the operation of each of the swing cylinders 38 is limited, but the flow rate Q required for the operation of the remaining hydraulic actuators 36, 37 (attitude change actuators 14) is controlled within the range of ３７ , Q ３６ Therefore, the operation of the attitude changing actuator 14 is not restricted.

[0115] Although not shown in the figure, the flow rate control unit 173 controls the flow rate Q ３８ When the flow rate Q of the lower limit is decreased to the lower limit, ３８ The flow rate Q of hydraulic oil that can be supplied to the four first hydraulic cylinders 36 with the next lowest operating priority while maintaining the ３６ At this time, the flow rate control unit 173 reduces the flow rate Q of the hydraulic motor 15 to the lower limit value. １５ The flow rate control unit 173 also maintains the reduced flow rate Q ３６ The four control valves 552 are controlled based on the above.

[0116] (Variation of Flow Rate Control) The flow rate control unit 173 sets the operation priority order as the operation priority of the other hydraulic actuators 15, 36, 38, but may also set weighting factors. The flow rate control unit 173 of this embodiment sets the weighting factor to a larger value as the operation priority becomes higher. For example, the flow rate control unit 173 sets the weighting factor of the first hydraulic cylinder 36 to "4," the weighting factor of the swing cylinder 38 to "3," and the weighting factor of the hydraulic motor 15 to "2."

[0117] FIG. 9 shows the total flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐ 9 is an explanatory diagram of flow rate control using a weighting coefficient when the total usage flow rate Q reaches t1. ｕｓｅ is the supplyable flow rate Q ｓｕｐ From the time t1, the flow rate control unit 173 controls the flow rate Q of the hydraulic oil secured for each of the hydraulic actuators 15, 36, and 38. １５ , Q ３８ , Q ３６ At this time, the flow rate control unit 173 reduces the flow rate ratio (Q １５ :Q ３８ :Q ３６ ) while maintaining the set weighting coefficient ratio (2:3:4), the flow rate Q of hydraulic oil to be secured １５ , Q ３８ , Q ３６ Reduces.

[0118] [Effects of the embodiment] According to the work vehicle 10 of this embodiment, the control device 17 (flow rate control unit 173) calculates the required flow rate Q of hydraulic oil required to operate the second hydraulic cylinder 37 to maintain the vehicle body 11 in a horizontal position. ３７ After ensuring the above, the control valves 551, 552, and 554 are controlled to adjust the flow rate of the hydraulic oil supplied to the other hydraulic actuators 15, 36, and 38. As a result, the total usage flow rate Q of the hydraulic oil used by all the hydraulic actuators 15, 36, 37, and 38 is ｕｓｅ is the supplyable flow rate Q of the hydraulic oil discharged by the hydraulic pump 54. ｓｕｐ Even if the required flow rate Q of the second hydraulic cylinder 37 is reached, ３７ is ensured, the vehicle body 11 can be maintained in a horizontal position.

[0119] The control device 17 calculates the total usage flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐThe control valves 551, 552, and 554 are controlled so as to adjust the flow rate of the hydraulic oil supplied to the hydraulic actuators 15, 36, and 38 other than the second hydraulic cylinder 37 within a range not exceeding the total usage flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐ It is possible to prevent the temperature from exceeding .

[0120] The control device 17 sets the operation priorities of the first hydraulic cylinder 36, the swing cylinder 38, and the hydraulic motor 15 according to the driving conditions detected by the driving condition detection unit (inclination sensor S4, operation switch 19). The control device 17 then controls the corresponding control valves to adjust the flow rate of hydraulic oil supplied to hydraulic actuators with lower operating priorities, after ensuring the flow rate of hydraulic oil necessary to operate the hydraulic actuators with higher operating priorities. This makes it possible to appropriately control the flow rates of hydraulic oil supplied to the first hydraulic cylinder 36, the swing cylinder 38, and the hydraulic motor 15 according to the driving conditions of the work vehicle 10.

[0121] The control device 17 calculates the total usage flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐ When the total usage flow rate Q reaches the maximum, the flow rate of the hydraulic oil secured for the other hydraulic actuators 15, 36, 38 is reduced in order of lowest priority, and the corresponding control valves are controlled based on the reduced flow rate. This prevents the operation of the hydraulic actuators with high priority from being restricted while maintaining the total usage flow rate Q ｕｓｅ is the supplyable flow rate Q ｓｕｐ It is possible to prevent the temperature from exceeding .

[0122] The control device 17 determines the flow rate Q to be secured for the hydraulic actuator 15 (38) with a low operating priority. １５ (Q ３８ ) to the lower limit, the flow rate Q １５ (Q ３８ ) while maintaining the flow rate Q ３８ (Q ３６This makes it possible to prevent the flow rate from falling below the lower limit when reducing the flow rate of hydraulic oil secured for the hydraulic actuator with a low operation priority.

[0123] When the detection result of the tilt sensor S4 indicates that the ground is flat, the control device 17 sets the operation priority of the swing cylinder 38 higher than the operation priority of the first hydraulic cylinder 36 and the hydraulic motor 15. This ensures that when the work vehicle 10 travels on flat ground, the flow rate of hydraulic oil necessary to operate the swing cylinder 38 involved in the travel is sufficient, thereby preventing restrictions on the swing operation of the work vehicle 10.

[0124] When the detection result of the inclination sensor S4 indicates that the vehicle is on uneven terrain, the control device 17 sets the operation priority of the first hydraulic cylinder 36 higher than the operation priority of the swing cylinder 38 and the hydraulic motor 15. This ensures that when the vehicle 10 is traveling on uneven terrain, the flow rate of hydraulic oil necessary for the operation of the first hydraulic cylinder 36, which is involved in maintaining the attitude of the vehicle body 11, is sufficient. This prevents restrictions on the operation of the first hydraulic cylinder 36 as well as the second hydraulic cylinder 37, making it even easier to maintain the vehicle body 11 in a horizontal attitude.

[0125] When the detection result of the inclination sensor S4 is flat ground, the control device 17 determines the required flow rate Q of the hydraulic oil to be secured for the second hydraulic cylinder 37. ３７ As a result, when the vehicle 10 is traveling on flat ground, the required flow rate Q of hydraulic oil secured for the second hydraulic cylinder 37 is reduced. ３７ Since the flow rate of hydraulic oil to other hydraulic actuators is reduced, the flow rate of hydraulic oil to other hydraulic actuators can be increased.

[0126] When the detection result of the inclination sensor S4 indicates that the ground is uneven, the control device 17 determines the required flow rate Q ３７ As a result, when the vehicle 10 is traveling on rough ground, the required flow rate Q of the hydraulic oil secured for the second hydraulic cylinder 37 is increased. ３７ Since the load increases, the vehicle body 11 can be reliably maintained in a horizontal position.

[0127] When the operation switch 19 is switched to high speed, the control device 17 sets the operation priority of each of the hydraulic motor 15 and the swing cylinder 38 higher than the operation priority of the first hydraulic cylinder 36. As a result, when the work vehicle 10 travels at high speed, the flow rate Q of hydraulic oil required to operate each of the hydraulic motor 15 and the swing cylinder 38 involved in the travel is １５ , Q ３８ Since this ensures that the vehicle 10 can travel at high speeds and perform turning movements, restrictions on the vehicle's ability to turn can be reduced.

[0128] When the operation switch 19 is switched to low speed, the control device 17 sets the operation priority of the first hydraulic cylinder 36 higher than the operation priority of the swing cylinder 38 and the hydraulic motor 15. As a result, when the work vehicle 10 is traveling at low speed, the flow rate Q of hydraulic oil required for the operation of the first hydraulic cylinder 36, which is involved in maintaining the attitude of the vehicle body 11, is set to ３６ This makes it possible to prevent the operation of the first hydraulic cylinder 36 as well as the second hydraulic cylinder 37 from being restricted, making it even easier to maintain the vehicle body 11 in a horizontal position.

[0129] [Others] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of the claims and equivalents thereof.

[0130] 10 Work vehicle 11 Vehicle body 12 Wheels 15 Hydraulic motor (hydraulic actuator for traveling) 17 Control device 19 Operation switch (traveling condition detection unit) 30 Bending link mechanism (vehicle body support unit) 36 First hydraulic cylinder (hydraulic actuator for forward and backward movement) 37 Second hydraulic cylinder (hydraulic actuator for up and down movement) 38 Swing cylinder (hydraulic actuator for swing) 54 Hydraulic pump 55 Control valve (flow rate adjustment valve) Q ３７ Flow rate (required flow rate) Q ｓｕｐ Available flow rate Q ｕｓｅ Total flow rate used S4 Inclination sensor (driving condition detection section)

Claims

1. A work vehicle comprising: a vehicle body; a plurality of wheels arranged on each of the left and right sides of the vehicle body; a plurality of vehicle body support parts that can change the distance between the contact surface of each of the wheels and the vehicle body; a plurality of hydraulic actuators including a vertical movement hydraulic actuator that drives the vehicle body support parts so as to change the distance in the vertical direction to maintain the vehicle body in a predetermined attitude; a hydraulic pump that discharges hydraulic oil to operate each of the plurality of hydraulic actuators; a plurality of flow rate adjustment valves that adjust the flow rate of hydraulic oil from the hydraulic pump to each of the hydraulic actuators; and a control device that controls each of the plurality of flow rate adjustment valves, wherein the control device controls the flow rate adjustment valves to adjust the flow rate of hydraulic oil supplied to the other hydraulic actuators after ensuring the required flow rate of hydraulic oil necessary for the operation of the vertical movement hydraulic actuator.

2. A work vehicle as described in claim 1, wherein the control device calculates the supplyable flow rate of hydraulic oil that can be supplied to the plurality of hydraulic actuators from the discharge flow rate of hydraulic oil discharged from the hydraulic pump, calculates the total usage flow rate of hydraulic oil actually used by each of the plurality of hydraulic actuators, and controls the flow control valve to adjust the flow rate of hydraulic oil supplied to the other hydraulic actuators within a range where the total usage flow rate does not exceed the supplyable flow rate.

3. A work vehicle as described in claim 2, further comprising a driving condition detection unit that detects the driving condition of the work vehicle, wherein the plurality of hydraulic actuators include, as the other hydraulic actuators, a forward / backward movement hydraulic actuator that drives the vehicle body support unit to change the distance in the forward / backward direction, a turning hydraulic actuator for turning the wheels relative to the vehicle body support unit, and a traveling hydraulic actuator that drives the wheels, and wherein the control device sets operation priorities of the forward / backward movement hydraulic actuator, the turning hydraulic actuator, and the traveling hydraulic actuator according to the driving condition detected by the driving condition detection unit, and controls the flow rate adjustment valve to adjust the flow rate of hydraulic oil supplied to the hydraulic actuators with a lower operation priority after ensuring the flow rate of hydraulic oil necessary for the operation of the hydraulic actuators with a higher operation priority.

4. A work vehicle as described in claim 3, wherein when the total usage flow rate reaches the supplyable flow rate, the control device reduces the flow rate of hydraulic oil secured in order from the hydraulic actuator with the lowest operating priority, and controls the flow control valve based on that flow rate.

5. A work vehicle as described in claim 4, wherein when the control device reduces the flow rate of hydraulic oil secured for the hydraulic actuator with the low operation priority to a lower limit value, it reduces the flow rate of hydraulic oil secured for the hydraulic actuator with the next lowest operation priority while maintaining the flow rate at the lower limit value, and controls the flow control valve based on the reduced flow rate.

6. A work vehicle as described in any one of claims 3 to 5, wherein the driving condition detection unit detects whether the road surface on which the work vehicle is traveling is flat or uneven, and when the detection result of the driving condition detection unit is flat, the control device sets the operation priority of the turning hydraulic actuator higher than the operation priority of the forward / rearward movement hydraulic actuator and the traveling hydraulic actuator.

7. A work vehicle as described in any one of claims 3 to 6, wherein the driving condition detection unit detects whether the road surface on which the work vehicle is traveling is flat or rough, and when the detection result of the driving condition detection unit indicates rough ground, the control device sets the operation priority of the forward / rearward movement hydraulic actuator higher than the operation priority of the turning hydraulic actuator and the traveling hydraulic actuator.

8. A work vehicle as described in claim 6 or claim 7, wherein the control device relatively reduces the required flow rate to be secured for the vertical movement hydraulic actuator when the detection result of the driving condition detection unit indicates flat ground, and relatively increases the required flow rate to be secured for the vertical movement hydraulic actuator when the detection result of the driving condition detection unit indicates rough ground.

9. A work vehicle as described in any one of claims 3 to 8, wherein the driving condition detection unit includes an operation switch that switches the driving speed of the work vehicle between high and low speeds, and when the operation switch is switched to high speed, the control device sets the operation priority of each of the driving hydraulic actuator and the turning hydraulic actuator to be higher than the operation priority of the forward / rearward movement hydraulic actuator.

10. A work vehicle as described in any one of claims 3 to 9, wherein the driving condition detection unit includes an operation switch that switches the driving speed of the work vehicle between high and low speeds, and when the operation switch is switched to low speed, the control device sets the operation priority of the forward / reverse movement hydraulic actuator higher than the operation priorities of the swing hydraulic actuator and the traveling hydraulic actuator.

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